Many former American and Chinese officials were reunited in Beijing, this week, for a two-day conference commemorating the 30th anniversary of the establishment of relations between the two countries. Although the focus was on cooperation, officials from both sides also highlighted some contentious issues that have threatened the relationship or could pose future threats.

Tang Jiaxuan was China's Foreign Affairs minister from 1998 to 2003. Speaking through an interpreter, he said both countries have always been able to work out their problems.

"This decade, marked by the turn of the century, has been extraordinary for China-US relations," he said.

Tang spoke at a conference in Beijing that brought together a group of former Chinese and American officials who were all active in developing relations between the two countries.

Joseph Prueher was U.S. ambassador to China, from 1999 to 2001. The most confrontational incident during his term involved the collision of U.S. and Chinese spy planes, near China's southern Hainan island.

He told journalists Washington and Beijing should be given credit for not handling the incident in a way that could have been divisive.

"Both governments decided and chose to handle this in a way that we will handle this between people that had respect for each other, in a constructive way, with a constructive outcome, handling an unfortunate event in a constructive way, so it provided an impetus for better relations rather than worse," said Prueher.

Another major sticking point in relations was the Chinese government's bloody crackdown on demonstrators in and around Beijing's Tiananmen Square, on June 4, 1989. Chinese army troops killed hundreds of protesters and bystanders.

To this day, the Chinese government calls the demonstrations a counter-revolutionary rebellion and says troops had to crack down to prevent chaos and maintain social order.

Winston Lord had just completed his term as American ambassador to China and left the country when the 1989 demonstrations started. He describes the events of that year as "significant."

"In the seven weeks of demonstrations, there were sometimes a million people on the streets, from all walks of life, not just students - party members, journalists, academics, military members, peasants, workers," Lord. "There wasn't one window broken in seven weeks, and there were demonstrations in 250 cities, not just Beijing. So, I think it was a momentous event."

The one US-China issue that has been sensitive from the very beginning is Taiwan. Lord says this was especially true when he was working with then President Richard Nixon and National Security Adviser Henry Kissinger on rapprochement with China in the 1970's.

The Nationalist government in Taipei fled to the island in 1949, after losing a civil war to the Communists.

When Washington formally recognized Beijing, in 1979, it severed its diplomatic recognition of Taipei.

Cross-straits tensions have eased a bit, following the April election of Taiwanese President Ma Ying-jeou. As a negotiating partner, China favors President Ma over his predecessor, the independence-minded Chen Shui-bian.

Mr. Lord says the Sino-American challenges in the near future will likely be economic. He says the global financial crisis means that both countries are in danger of resorting to contentious policies.

For American officials, the Chinese currency is a problem. Washington has accused China of artificially keeping its currency undervalued, to help Chinese exports.

"In turn, you have a new administration coming in, and the Democrats tend to be more protectionist than Republicans," said Lord. "I don't believe Mr. Obama is, but if they see China resorting to these measures, and we already have a tremendous trade deficit and have lost some jobs to China, then the U.S. could resort to trade protectionism."

Chinese Vice-Premier Xi Jinping says he hopes the two countries become, in his words, "cooperative partners, not strategic competitors."

Xi says the Sino-American relationship is beneficial to both countries and is not a short-term competition. He says that a good Chinese-American relationship not only benefits the two countries, but is good for the entire world.